Currently, researches and commercialization of a point of care (POC) and a lab-on-a-chip (LOC) (which means a laboratory on a chip and is a technology for diagnosing various diseases in a small chip at a time) are actively carried out in the field of bio-industry. The LOC makes the experiment equipments used in various field such as, biology, medical science, pharmacology, and so on to be embodied on a single plastic micro-chip. Using the micro-chip, information of every single cells or particles existing in body fluids or solutions could be obtained and examined.
In order to obtain information on cells or particles, cells (particles) should be flowed in a line in the channel. To make it possible, the process of focusing the fluid which contains the cells (particles) to pass through only a fixed area is necessary.
Conventional focusing channel has a nozzle the width of which is narrowed in symmetry on both right and left sides of the channel. Due to the symmetry of both sides of the channel, cells (particles) entering the symmetrically narrowing channel simultaneously block the focusing channel, or two cells (particles) are combined into one cell and flow as one cell. Thus, bottleneck phenomenon occurs as such.
FIG. 1 is a photograph of red blood cells flowing in a conventional focusing channel composed of symmetric fixed walls. In FIG. 1, the oval mark indicates a point where two red blood cells enter the focusing channel at the same time and the bottleneck phenomenon occurs due to the symmetric shape of left and right walls in the focusing channel.
FIG. 2 is a photograph of red blood cells flowing in a conventional focusing channel composed of symmetric fluid walls. In FIG. 2, two red blood cells also enter the focusing channel at the same time and the bottleneck phenomenon occurs due to the symmetric shape of left and right fluid walls in the focusing channel similarly to the case of FIG. 1.
These situations of blockage and combination of two cells (particles) into one in the focusing channel may cause an error in data analysis, and eventually deteriorate efficiency of the analysis devices. For instance, in the focusing channel used in device for diagnosis of cancer or diabetes by examining the flow velocity of red blood cells, above defects may cause the slowdown of flow velocity. Thus, it may be impossible to diagnose such disease precisely.
The ‘fixed wall’ used herein means an actual solid wall formed on a plastic micro-chip in designing and manufacturing of the micro-chip.
The term ‘fluid wall’ means a wall of fluid state. It does not form an actual wall in the micro chip. However, when flowing the fluids containing particles to be observed in the channel, buffer solution is also flowed in the left and right sides of the flowing fluids, and thereby the buffer solution serves as a wall. FIG. 3 shows a focusing process for fluids using the fluid wall.